Methyl Thiocyanate Research Articles

Anionic Effects on Concentrated Aqueous Lithium Ion Dynamics.

The dynamics, orientational anisotropy, diffusivity, viscosity, and density were measured for concentrated lithium salt solutions, including lithium chloride (LiCl), lithium bromide (LiBr), lithium nitrite (LiNO2), and lithium nitrate (LiNO3), with methyl thiocyanate as an infrared vibrational probe molecule, using two-dimensional infrared spectroscopy (2D IR), nuclear magnetic resonance (NMR) spectroscopy, and viscometry. The 2D IR, NMR, and viscosity results show that LiNO2 exhibits longer correlation times, lower diffusivity, and nearly 4 times greater viscosity compared to those of the other lithium salt solutions of the same concentration, suggesting that nitrite anions may strongly facilitate structure formation via strengthening water-ion network interactions, directly impacting bulk solution properties at sufficiently high concentrations. Additionally, the LiNO2 and LiNO3 solutions show significantly weakened chemical interactions between the lithium cations and the methyl thiocyanate when compared with those of the lithium halide salts.

Immunochromatographic assay for detection (2-benzothiazolylthio) methyl thiocyanate in food packaging paper materials

The residue of fungicides in food packaging paper materials is one of the important factors leading to food safety problems, which poses a serious threat to public health. (2-benzothiazolylthio) methyl thiocyanate (TCMTB) is an important anti-mildew fungicide, which is widely used in wood and paper industry. In order to ensure the health of consumers, it is of great significance to establish an efficient and sensitive rapid detection method for TCMTB in food packaging materials. In this study, we prepared monoclonal antibody (mAb) against TCMTB with the IC50 value of 7.60 ng/mL, and subsequently developed an immunochromatographic assay (ICA) strip based on the mAb for the rapid detection of TCMTB residues. The calculated detection limit of the ICA strip in food packaging paper was 3.20 ng/g, and the recovery rate was within an acceptable range, ranging from 97.7% to 102.7%. Therefore, the developed ICA is expected to realize the rapid screening of TCMTB residues in food packaging paper.

Understanding into interfacial properties and reactivity of COFs toward accelerating Menshutkin SN2 reaction

Given the poor understanding about the effects of confined polar microenvironment on interfacial behaviors of Menshutkin SN2 reaction, herein, the interfacial properties and reactivities between 1-methylimidazole and methyl thiocyanate reaction induced by interfacial polar microenvironments of covalent organic frameworks (COFs) with varying pore size and functional groups were investigated using in situ Fourier transform infrared spectroscopy, molecular dynamics simulations, and metadynamics calculations. The decreased nanopore size of COFs from 3.2 to 1.2 nm can enlarge reaction rates (k) and reduce activation energy barriers (ΔE*). The hydroxyl-modified COF (2.8 nm) can further cause larger k and lower ΔE* by 6.1 and 0.8 kJ/mol compared to the bulk and smaller pore-size COF (1.2 nm) system, respectively, mainly originating from induced higher aggregation, preferred orientation, and the stabilization of charge separation of transition state. This work provides a systematic understanding for the confined interfacial properties toward accelerating the Menshutkin reaction.

Experimental two-dimensional infrared spectra of methyl thiocyanate in water and organic solvents.

Thiocyanates, nitriles, and azides represent a versatile set of vibrational probes to measure the structure and dynamics in biological systems. The probes are minimally perturbative, the nitrile stretching mode appears in an otherwise uncongested spectral region, and the spectra report on the local environment around the probe. Nitrile frequencies and lineshapes, however, are difficult to interpret, and theoretical models that connect local environments with vibrational frequencies are often necessary. However, the development of both more accurate and intuitive models remains a challenge for the community. The present work provides an experimentally consistent collection of experimental measurements, including IR absorption and ultrafast two-dimensional infrared (2D IR) spectra, to serve as a benchmark in the development of future models. Specifically, we catalog spectra of the nitrile stretching mode of methyl thiocyanate (MeSCN) in fourteen different solvents, including non-polar, polar, and protic solvents. Absorption spectra indicate that π-interactions may be responsible for the line shape differences observed between aromatic and aliphatic alcohols. We also demonstrate that a recent Kamlet-Taft formulation describes the center frequency MeSCN. Furthermore, we report cryogenic infrared spectra that may lead to insights into the peak asymmetry in aprotic solvents. 2D IR spectra measured in protic solvents serve to connect hydrogen bonding with static inhomogeneity. We expect that these insights, along with the publicly available dataset, will be useful to continue advancing future models capable of quantitatively describing the relation between local environments, line shapes, and dynamics in nitrile probes.

Genotypes of Eruca vesicaria subsp. sativa grown in contrasting field environments differ on transcriptomic and metabolomic levels, significantly impacting nutritional quality.

Rocket (Eruca vesicaria subsp. sativa) is a source of sulfur-containing glucosinolates (GSLs). GSLs and their breakdown hydrolysis products (GHPs) are responsible for health-related benefits, such as anti-cancer and anti-neurodegenerative properties. Understanding how phytochemical composition changes between cultivation environments is key to developing cultivars with improved nutritional quality. Two consecutive harvests (first and second regrowth) of crops, grown in both Italy and the UK, were used to determine the phytochemical and transcriptomic differences between six lines of Eruca. Samples were taken upon delivery from field sites (D0) and after five days of cold storage (D5) for each location. Leaves were analysed for sulfur content, volatile organic compounds (VOCs), GSLs, GHPs, and sugars. Transcriptome data were associated with metabolite profiles to identify differentially expressed genes between plants grown in the two environments. VOC compounds (carbon disulfide, methyl thiocyanate) were associated with growth environment and with differences in sulfur metabolism gene expression (APR2, LSU2, LSU3, SDI1, SiR), GSL biosynthesis (MYB28, FMOGS-OX2) and GHP formation (ESM1, TGG1, TGG2). The concentrations of sugars were an order of magnitude greater in UK grown samples (up to 29.9 mg g-1 dry weight; dw). Sulfur content was significantly higher in the Italy plant samples (11.4 - 20.1 mg g-1 dw), which was in turn associated with higher concentrations of GSLs (pentyl GSL, up to 15.8 μmol g-1 dw; sinigrin, up to 0.005 μmol g-1 dw; glucoraphanin, up to 5.1 μmol g-1 dw; glucorucolamine, up to 23.6 μmol g-1 dw; neoglucobrassicin, up to 5.3 μmol g-1 dw) and hydrolysis products (sativin, up to 13.5 μmol g-1 dw; erucin, up to 1 μmol g-1 dw; sulforaphane, up to 34.7 μmol g-1 dw). VOC profiles of plants cultivated in the UK were distinct from Italy grown plants, with higher relative abundances of alkanes and esters in second cut and shelf-life (D5) samples. The data indicate a significant interaction of cultivar response with environment, highlighting the difficulty of producing Eruca crops with consistent phytochemical and postharvest traits. Genes with differential expression between plants grown in Italy and the UK could be used as markers of phytochemical quality and composition.

Extracting accurate infrared lineshapes from weak vibrational probes at low concentrations

Fourier-transform infrared (FTIR) spectroscopy using vibrational probes is an ideal tool to detect changes in structure and local environments within biological molecules. However, challenges arise when dealing with weak infrared probes, such as thiocyanates, due to their inherent low signal strengths and overlap with solvent bands. In this protocol we demonstrate:•A streamlined approach for the precise extraction of weak infrared absorption lineshapes from a strong solvent background.•A protocol combining a spectral filter, background modeling, and subtraction.•Our methodology successfully extracts the CN stretching mode peak from methyl thiocyanate at remarkably low concentrations (0.25 mM) in water, previously a challenge for FTIR spectroscopy.This approach offers valuable insights and tools for more accurate FTIR measurements using weak vibrational probes. This enhanced precision can potentially enable new approaches to enhance our understanding of protein structure and dynamics in solution.

Identification of glucosinolates and volatile odor compounds in microwaved radish (Raphanus sativus L.) seeds and the corresponding oils by UPLC-IMS-QTOF-MS and GC × GC-qMS analysis

The effect of microwave treatment on the content of glucosinolates (GSL) in radish seeds and volatile odor compounds in the microwaved radish seed oils (MRSO) is still unclear. In this study, a total of 13 GSL were identified and quantified in five radish seed varieties by UPLC-IMS-QTOF-MS, among which glucoraphenin, glucoraphasatin, glucoerucin accounting for up to 90 %. Total GSL decreased by 47.39–67.88% after microwave processing. Moreover, 58 odor compounds were identified in MRSO, including 6 sulfides, 12 nitriles, 2 isothiocyanates, 10 alcohols, 12 aldehydes, 5 ketones, 6 acids, and 5 others. The major odor compounds were (methyldisulfanyl)methane, dimethyltrisulfane, (methylsulfinyl)methane, 3-(methylsulfanyl)-1-propanol, methyl thiocyanate, hexanenitrile, 5-(methylsulfanyl)pentanenitrile, and 4-isothiocyanato-1-butene with odor activity value (OAV) higher than 1. The principal components analysis (PCA) results can distinguish MRSO from five different radish seed varieties, three of which (H20-18, H20-19 and H20-28) were in one group and other two (H20-23 and H20-26) were in another group. In addition, aliphatic GSL showed positive correlations with sulfides, isothiocyanates, and nitriles, while negative correlations with alcohols. This work provides a new insight into the odor contribution of GSL degradation products.

Antagonistic Activity of Volatile Organic Compounds Produced by Acid-Tolerant Pseudomonas protegens CLP-6 as Biological Fumigants To Control Tobacco Bacterial Wilt Caused by Ralstonia solanacearum.

Tobacco bacterial wilt, which is caused by Ralstonia solanacearum, is a devastating soilborne disease of tobacco worldwide and is widespread in the continuously acidic fields of southern China. Here, the fumigation activity under different pH conditions, component identification, and bioactivity of the volatile organic compounds (VOCs) produced by an acid-tolerant strain, Pseudomonas protegens CLP-6, were investigated. There was a wide antimicrobial spectrum of the VOCs against phytopathogens, including four bacteria, eight fungi, and two oomycetes. The antagonistic activity of the VOCs against R. solanacearum was proportionally correlated with the concentration of the inoculum, amount, culture time, and culture pH for CLP-6. The number of gene copies of R. solanacearum was significantly inhibited by VOCs produced at pH 5.5 in vivo. The control effect of VOCs emitted at pH 5.5 was 78.91% for tobacco bacterial wilt, which was >3-fold greater than that at pH 7.0. Finally, the main volatile compounds were identified by solid-phase microextraction (SPME)-gas chromatography-mass spectroscopy (GC-MS) as S-methyl thioacetate, methyl thiocyanate, methyl disulfide, 1-decene, 2-ethylhexanol, 1,4-undecadiene, 1-undecene, 1,3-benzothiazole, and 2,5-dimethylpyrazine, and the inhibition rates of 1,3-benzothiazole, 2-ethylhexanolmethyl thiocyanate, dimethyl disulfide, and S-methyl thioacetate were 100%, 100%, 88.91%, 67.64%, and 53.29%, respectively. S-Methyl thioacetate was detected only at pH 5.5. In summary, VOCs produced by P. protegens CLP-6 had strong antagonistic activities against phytopathogens, especially R. solanacearum, under acidic conditions and could be used to develop a safe and additive fumigant against R. solanacearum on tobacco and even other Solanaceae crop bacterial wilt diseases in acidic fields. IMPORTANCE VOCs produced by beneficial bacteria penetrate the rhizosphere to inhibit the growth of plant-pathogenic microorganisms; thus, they have the potential to be used as biological agents in controlling plant diseases. Tobacco bacterial wilt, which is caused by the acidophilic pathogen R. solanacearum, is a major bacterial disease in southern China and is prevalent in acidic soil. In this study, we discovered that the VOCs produced by P. protegens CLP-6 had excellent inhibitory effects on important plant pathogens. Moreover, two of the VOCs, namely, 1,3-benzothiazole and 2-ethylhexanol, had excellent inhibitory effect on R. solanacearum, and another VOC substance, methyl thiocyanate, was produced only at pH 5.5. The VOCs produced by the acid-tolerant strain P. protegens CLP-6 may have potential as environment-friendly microbial fumigant agents for bacterial wilt of tobacco or even other Solanaceae crops in acidic soils in China.

Moving the corpse to hide the evidence: horizontal as well as vertical movement is important when burying beetles cache a carcass

Being the first to discover a resource can provide a competitive advantage (priority effect), even for an animal that is inferior in aggressive contests. Nicrophorus spp. (burying beetles) are known for caching a small vertebrate carcass as provision for their young, reducing volatile cues available to rivals by burying the carcass (vertical movement) and by altering the microbial community. A decomposing carcass, however, can leave cues (residues of decay) on soil and leaf litter that a burying beetle has less opportunity to neutralize. I investigated whether horizontal movement of the carcass by burying beetles, separating the carcass from soil at the site of death, might reduce competition from congeners. When fresh carcasses were placed in the field on top of soil with residues of decay, akin to no horizontal displacement, carcasses were discovered within 24 h by free-flying competitors more frequently (58.2%) than when the carcass was placed 1 m from treated soil (8.3%). In a second experiment, carcasses were more likely to be discovered by burying beetles when a chemical attractant (methyl thiocyanate) was placed near a carcass (0.03 and 0.25 m) than when it was placed more distant (1 and 5 m) or for controls (no attractant). The results suggest that horizontal displacement of a carcass after discovery serves not only to locate a suitable spot for burial but also to reduce information available to rivals searching for the resource.

Origin of thiocyanate spectral shifts in water and organic solvents.

Vibrational spectroscopy is a useful technique for probing chemical environments. The development of models that can reproduce the spectra of nitriles and azides is valuable because these probes are uniquely suited for investigating complex systems. Empirical vibrational spectroscopic maps are commonly employed to obtain the instantaneous vibrational frequencies during molecular dynamics simulations but often fail to adequately describe the behavior of these probes, especially in its transferability to a diverse range of environments. In this paper, we demonstrate several reasons for the difficulty in constructing a general-purpose vibrational map for methyl thiocyanate (MeSCN), a model for cyanylated biological probes. In particular, we found that electrostatics alone are not a sufficient metric to categorize the environments of different solvents, and the dominant features in intermolecular interactions in the energy landscape vary from solvent to solvent. Consequently, common vibrational mapping schemes do not cover all essential interaction terms adequately, especially in the treatment of van der Waals interactions. Quantum vibrational perturbation (QVP) theory, along with a combined quantum mechanical and molecular mechanical potential for solute-solvent interactions, is an alternative and efficient modeling technique, which is compared in this paper, to yield spectroscopic results in good agreement with experimental FTIR. QVP has been used to analyze the computational data, revealing the shortcomings of the vibrational maps for MeSCN in different solvents. The results indicate that insights from QVP analysis can be used to enhance the transferability of vibrational maps in future studies.

Synthesis of Diamantane Derivatives in Nitric Acid Media

1-Mono- and 1,4-difunctional diamantane derivatives were synthesized by the reaction of diamantane with nitric acid or a HNO3–AcOH mixture followed by the addition of nitrogen-containing nucleophiles. Methyl N-(diamantan-1-yl)carbamothioate was synthesized from diamantan-1-ol and methyl thiocyanate in sulfuric acid.

Finding a fresh carcass: bacterially derived volatiles and burying beetle search success

When burying beetles first emerge as adults, they search for well-rotted carcasses with fly maggots on which to feed. After attaining reproductive competence, they switch their search and respond to a small, fresh carcass to prepare for their brood. Because the cues used to locate a feeding versus a breeding resource both originate from carrion, the beetles must respond to subtle changes in volatiles during decomposition. We investigated cues used to locate a fresh carcass in the field by (1) a general subtractive method, applying an antibacterial or antifungal compound to reduce microbially derived volatiles, and (2) a specific additive method, placing chemical supplements near a fresh carcass. Five sulfur-containing compounds, known to result from bacterial metabolism of sulfur-containing amino acids, were studied: dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), methyl thiolacetate (MeSAc, also known as S-methyl thioacetate), and methyl thiocyanate (MeSCN). When a carcass aged for 48 h was treated with an antibacterial compound to reduce volatiles, there was a 59% decrease in beetles discovering the resource. The addition of the chemical supplement MeSAc had no effect on discovery of a fresh carcass, while DMS and DMDS had a limited ability to attract breeding beetles. The chemical that was least well known, MeSCN, increased beetle numbers by 200–800% on a fresh carcass and almost guaranteed discovery. DMTS, which is known to attract a variety of carrion insects, was the only compound to significantly reduce beetle presence at a fresh carcass. A laboratory experiment demonstrated that DMTS does not directly inhibit breeding, suggesting that DMTS deters breeding beetles while they fly.

Enhanced Menshutkin SN2 Reactivity in Mesoporous Silica: The Influence of Surface Catalysis and Confinement.

A significant enhancement in the Menshutkin SN2 reaction between 1-methylimidazole (MeIm) and methyl thiocyanate (MeSCN) is observed when the reaction is confined in the nanoscale silica pores of MCM41 and SBA15. The experiments in the silica pores are conducted without the surrounding bulk reaction mixture. The influences of temperature, pore radius, and surface chemistry on the kinetics of the confined reaction are analyzed with time-dependent infrared spectroscopy, molecular dynamics simulations, and ab initio calculations. The rate constant of the pseudo-first order reaction increases with decreasing pore size, and the activation energy is found to decrease by 5.6 kJ/mol in the smallest pore studied (2.8 nm) relative to the bulk reaction. The rate constant dependence on pore size is accurately described by a two-state model in which molecules within the 4.6 Å interfacial layer experience a 2.4-fold rate constant increase relative to those reacting at the bulk rate further away from the interface. The removal of polar silanol groups from the silica surface via passivation with trimethylsilyl chloride results in bulk-like kinetics despite a reduction in the pore diameter, demonstrating the role of silanols as catalytic sites. Electronic structure calculations of the energy profile on a model silica surface confirm that silanol groups, particularly those of the vicinal type, can reduce the activation energy and reaction endothermicity through the donation of hydrogen bonds to the reactant, transition state, and product complexes.

Dynamics of Water Molecules and Ions in Concentrated Lithium Chloride Solutions Probed with Ultrafast 2D IR Spectroscopy.

Water and ion dynamics in concentrated LiCl solutions were studied using ultrafast 2D IR spectroscopy with the methyl thiocyanate (MeSCN) CN stretch as the vibrational probe. The IR absorption spectrum of MeSCN has two peaks, one peak for water associated with the nitrogen lone pair of MeSCN (W) and the other peak corresponding to Li+ associated with the lone pair (L). To extract the spectral diffusion (structural dynamics) of W and L species, we developed a method that isolates the peak of interest by subtracting the 2D Gaussian proxies of multiple interfering peaks. Center line slope data (normalized frequency-frequency correlation function) for 2D bands from the W and L are fit with triexponential functions. The fastest component (1.1-1.6 ps) is assigned to local hydrogen bond length fluctuations. The intermediate timescale (∼4.0 ps) corresponds to the hydrogen bond network rearrangement. The slowest component decays in ∼40 ps and corresponds to ion pair and ion cluster dynamics. The very similar W and L spectral diffusion indicates that the motions of the water and ions are strongly coupled. Orientational relaxations of the W and L species were extracted using a new method to eliminate the effects of overlapping peaks. The results show that MeSCN bound to water undergoes orientational relaxation significantly faster than MeSCN bound to Li+. The orientational and spectral diffusion results are compared. A Stark coupling model is used to extract the root mean square average electric field caused by the ion clouds along the CN moiety as a function of concentration.

Tracking Aqueous Proton Transfer by Two-Dimensional Infrared Spectroscopy and ab Initio Molecular Dynamics Simulations.

Proton transfer in water is ubiquitous and a critical elementary event that, via proton hopping between water molecules, enables protons to diffuse much faster than other ions. The problem of the anomalous nature of proton transport in water was first identified by Grotthuss over 200 years ago. In spite of a vast amount of modern research effort, there are still many unanswered questions about proton transport in water. An experimental determination of the proton hopping time has remained elusive due to its ultrafast nature and the lack of direct experimental observables. Here, we use two-dimensional infrared spectroscopy to extract the chemical exchange rates between hydronium and water in acid solutions using a vibrational probe, methyl thiocyanate. Ab initio molecular dynamics (AIMD) simulations demonstrate that the chemical exchange is dominated by proton hopping. The observed experimental and simulated acid concentration dependence then allow us to extrapolate the measured single step proton hopping time to the dilute limit, which, within error, gives the same value as inferred from measurements of the proton mobility and NMR line width analysis. In addition to obtaining the proton hopping time in the dilute limit from direct measurements and AIMD simulations, the results indicate that proton hopping in dilute acid solutions is induced by the concerted multi-water molecule hydrogen bond rearrangement that occurs in pure water. This proposition on the dynamics that drive proton hopping is confirmed by a combination of experimental results from the literature.

Employing thiocyanate salts as a nitrogen source via CN bond cleavage: divergent synthesis of α-ketoamides and 2-acyloxazoles

A switchable procedure for the synthesis of α-ketoamides and 2-acyloxazoles from aryl methyl ketones and thiocyanate salts is reported.

Ion-Molecule Complex Dissociation and Formation Dynamics in LiCl Aqueous Solutions from 2D IR Spectroscopy.

Ion-molecule complex dynamics as well as water dynamics in concentrated lithium chloride (LiCl) solutions are examined using ultrafast two-dimensional infrared (2D IR) spectroscopy with the CN stretching mode of methyl thiocyanate (MeSCN) as the vibrational probe. In pure water, MeSCN has a narrow symmetric absorption line shape. 2D IR spectral diffusion measurements of the CN stretch give the identical time dependence of water dynamics, as previously observed using the OD stretch of HOD in H2O. In concentrated LiCl solutions, the IR absorption spectrum of MeSCN displays two distinct peaks, one corresponding to water H-bonded to the N lone pair of MeSCN (W) and the other corresponding to Li+ associated with the N (L). These two species are in equilibrium, and switching of the CN bonding partner from Li+ to H2O and vice versa was observed and explicated with 2D IR chemical exchange spectroscopy. The MeSCN·Li+ complex dissociation time constant, τLW, and the MeSCN·H2O dissociation time constant, τWL, were determined. The observed τLW chemical exchange dissociation time constant changes from 60 to 40 ps as the LiCl concentration decreases from ∼10.7 to ∼7.7 M, mainly due to the increase of the water concentration as the LiCl concentration is reduced. The observed time constants are independent of the model for the chemical reaction. With the assumption of a simple chemical equation, MeSCN·Li+ + H2O ⇄ MeSCN·H2O + Li+, the equilibrium equation rate constants were obtained from the observed chemical exchange time constants. It was determined that the equilibrium rate constants barely change even though the viscosity changes by a factor of 2 and the ionic strength changes by a factor of 1.4. Extrapolation to dilute LiCl solution estimates the τLW to be ∼30 ps. The orientational relaxation (anisotropy decay) of both the W and L complexes was measured using polarization selective 2D IR experiments. The lithium-bonded species undergoes orientational relaxation ∼3 times slower than the water-bonded species in each LiCl solution studied. The difference demonstrates the distinct interactions with the medium experienced by the neutral and charged species in the concentrated salt solutions.

Contrast between the mechanisms for dissociative electron attachment to CH3SCN and CH3NCS.

The kinetics of thermal electron attachment to methyl thiocyanate (CH3SCN), methyl isothiocyanate (CH3NCS), and ethyl thiocyanate (C2H5SCN) were measured using flowing afterglow-Langmuir probe apparatuses at temperatures between 300 and 1000 K. CH3SCN and C2H5SCN undergo inefficient dissociative attachment to yield primarily SCN- at 300 K (k = 2 × 10-10 cm3 s-1), with increasing efficiency as temperature increases. The increase is well described by activation energies of 0.17 eV (CH3SCN) and 0.14 eV (C2H5SCN). CN- product is formed at <1% branching at 300 K, increasing to ∼30% branching at 1000 K. Attachment to CH3NCS yields exclusively SCN- ionic product but at a rate at 300 K that is below our detection threshold (k < 10-12 cm3 s-1). The rate coefficient increases rapidly with increasing temperature (k = 6 × 10-11 cm3 s-1 at 600 K), in a manner well described by an activation energy of 0.51 eV. Calculations at the B3LYP/def2-TZVPPD level suggest that attachment to CH3SCN proceeds through a dissociative state of CH3SCN-, while attachment to CH3NCS initially forms a weakly bound transient anion CH3NCS-* that isomerizes over an energetic barrier to yield SCN-. Kinetic modeling of the two systems is performed in an attempt to identify a kinetic signature differentiating the two mechanisms. The kinetic modeling reproduces the CH3NCS data only if dissociation through the transient anion is considered.

The antimicrobial volatile power of the rhizospheric isolate Pseudomonas donghuensis P482.

Soil and rhizosphere bacteria produce an array of secondary metabolites including a wide range of volatile organic compounds (VOCs). These compounds play an important role in the long-distance interactions and communication between (micro)organisms. Furthermore, bacterial VOCs are involved in plant pathogens inhibition and induction of soil fungistasis and suppressivenes. In the present study, we analysed the volatile blend emitted by the rhizospheric isolate Pseudomonas donghuensis P482 and evaluated the volatile effect on the plant pathogenic fungi and bacteria as well as one oomycete. Moreover, we investigated the role of the GacS/GacA system on VOCs production in P. donghuensis P482. The results obtained demonstrated that VOCs emitted by P. donghuensis P482 have strong antifungal and antioomycete, but not antibacterial activity. The production of certain volatiles such as dimethyl sulfide, S-methyl thioacetate, methyl thiocyanate, dimethyl trisulfide, 1-undecan and HCN is depended on the GacS/GacA two-component regulatory system. Apparently, these compounds play an important role in the pathogens suppression as the gacA mutant entirely lost the ability to inhibit via volatiles the growth of tested plant pathogens.

A theoretical study on the spectroscopy, structure, and stability of C2H3NS molecules

Here we report the results of a theoretical study devoted to the family of methyl thiocyanate (CH3–SCN) isomers. From among 14 species sharing the C2H3NS stoichiometry, the most thermodynamically stable of these are methyl isothiocyanate (CH3–NCS), methyl thiocyanate (CH3–SCN), and mercaptoacetonitrile (HS–CH2–CN). Energies were reliably predicted using the CCSD(T) variant of coupled-cluster calculations making use of a quadruple zeta-quality basis set. Minor contributions to the total energy, including scalar relativistic effects and extrapolation to the complete basis set limit, were obtained using second-order many-body perturbation theory. The three most stable isomers feature similar energy values (differing by few kJ/mol) that are much lower than those of the remaining C2H3NS species (more than 85 kJ/mol). Spectroscopic properties including rotational constants, anharmonic vibrational frequencies, infrared absorption intensities (harmonic), Raman activities, and the energies of excited electronic states have been derived using coupled-cluster or density functional theory for the whole set of C2H3NS molecules. Additionally, infrared absorption intensities and frequencies of overtone and combination bands are given for the three lowest energy isomers.